Please refer to FIG. 1, which is a circuit diagram showing a sensing conceptual scheme and precharge circuit in a conventional memory array according to the prior art. In FIG. 1, the control circuit of only one cell of a plurality of cells in a memory array is illustrated.
In FIG. 1, the sensing conceptual scheme 10 mainly includes an inverter 101 and a memory cell 102. The clamp transistor MCL has a first end electrically connected to the voltage source VDD through the load 103, a second end electrically connected to the input end of the inverter 101 and the bit line, and a control end electrically connected to the output end of the inverter 101. The memory cell 102 is controlled by the word-line voltage VWL. The capacitor CBL shown in the figure is only representative of a capacitor effect between the bit-line voltage VBL and the ground, which is not configured in the practical circuit topology as a real capacitor.
In the sensing conceptual scheme 10, the capacitance of the capacitor CBL is large since the bit line is long. For raising the bit-line voltage VBL to a predetermined value, e.g. 1.6 V, it will take a long time to stably raise the bit-line voltage VBL to the predetermined value only with the operation of the sensing conceptual scheme 10, which is a condition unable to satisfy the user.
To overcome this drawback, as shown in FIG. 1, an extra pre-charge path 11 is configured in the sensing conceptual scheme 10 in the prior art. The pre-charge is speeded up in the front end of the pre-charge phase by the extra pre-charge path 11 so as to raise the bit-line voltage VBL to the predetermined value more rapidly.
However, the operation of the extra pre-charge path 11 is controlled by the delay circuit 12 with a delay time which varies with power source, temperature and process corner. It is therefore difficult to control precisely the delay time of the delay circuit 12. That is to say, it is difficult to control precisely the start procedure, the operation procedure and the close procedure of the extra pre-charge path 11.